1. Field of the Invention
The present invention relates to a method and device for locating functional tissue areas in a tissue region, particularly in a brain tissue region. Additionally, the invention relates to a device for carrying out the method, an operation microscope and a computer program product.
2. Description of the Related Art
In the case of tumor operations in the brain with tumors in the vicinity of eloquent brain areas, i.e. functional brain areas, for example in the vicinity of the motor cortex, in the vicinity of sensorimotor centers, in the vicinity of the speech center, etc., the treating surgeon is torn between how radical the tumor removal should be and how to sustain functional brain tissue and thus optimize the post-operative quality of life of the patient. Very precise locating of the functional tissue areas is very important in this case.
These days, typical methods for locating functional brain areas are based on electrophysiological detection of these areas, for example by means of electric stimulation of certain skeletal muscles (e.g. the calf) and measuring a potential on the surface of the brain by means of applied electrodes. Thus, this is a method involving contact. However, such methods involving contact have limitations that limit the options for application. By way of example, the minimum possible size of the electrodes and the smallest possible electrode spacing determine the resolution when locating the functional tissue areas. This cannot achieve a high-resolution display of functional tissue areas. Furthermore, a method involving contact is inevitably associated with risks resulting from contacting the tissue with an object made of tissue-extraneous material.
In order to overcome the disadvantages of the described methods involving contact, U.S. Pat. No. 6,196,226 B1 or U.S. Pat. No. 5,215,095, for example, propose imaging functional areas of the brain by means of an optical image. In the methods described in these documents, the tissue region is recorded during a stimulation leading to a change in the physiological properties of the functional areas. The change in the physiological properties in turn leads to a change in the optical properties of reflected light. Thus, the difference between a stimulation image, recorded during the stimulation, and a comparison image, recorded without stimulation, is formed in order to display the functional areas, and the functional areas are located on the basis of the difference. The option of carrying out a 3D reconstruction of a tissue region has also been disclosed, in which a difference image from a recording with stimulation and a recording without stimulation is superposed with 3D data obtained by a previously recorded MRI data record. This type of display is intended to make it easier for the medical practitioner to locate a functional region correctly.
However, it is extremely difficult to carry out the optical imaging methods described in the aforementioned documents because the changes in the reflected light connected to the functional stimulation are of low intensity. Thus, in order to obtain usable images, a multiplicity of images with and without stimulation are generally recorded in the methods described at the outset, and there is averaging over all images with stimulation and averaging over all images without stimulation before the difference image is formed. Moreover, use is generally made of expensive monochromes (CCD cameras) with a high grayscale resolution (24 bit) and relatively long integration times. Locating functional tissue areas using this takes up relatively large amounts of time, which is particularly disadvantageous if this increases the duration of the operation.
Therefore, overall, it is very difficult to generate contrast-rich images of functional regions in a short time using the described optical imaging methods.
Thus, an object of the present invention can be considered the provision of an advantageous method and an advantageous device for locating functional tissue areas in a tissue region.
Moreover, an object of the invention can be considered the provision of an advantageous operation microscope.
The provision of a computer program product, which allows an automated procedure for locating functional tissue areas, can be considered a further object.